Transportation was revolutionized at the turn of the 20th century. The Great Horse Manure Crisis contributed to the revolution by revealing a problem with the use of horses in large cities. Even though horses had served humans well for thousands of years, their pollution in the late 1800s created an impetus for change.
San Francisco in the 1890s. EQUINE Ink.
San Francisco in 1906. San Francisco Film Museum.
The change is evident in these two photographs taken a little over a decade apart on Market Street in San Francisco. The photograph on the left was taken in the 1890s and shows the street covered in manure. The photograph on the right was taken just before the great earthquake in 1906. Instead of horses and carriages, automobiles are the mode of transportation and Market Street is notably cleaner.